1. Field of the Invention
This invention relates to a non-destructive assay for oxidative status of unsaturated lipids and to a method for evaluation of antioxidant effectiveness in lipid-polypeptide layers.
2. Description of the Prior Art
Lipids can become rancid as a result of oxidation. This rancidity caused by oxidation is a major cause of food deterioration. The acceptability of a food product often depends on the extent to which such deterioration has occurred. Therefore, some technique for assessing the extent of oxidation and for prediction of remaining storage life is necessary. Sensory analysis is one of the most sensitive methods available. However, this method is not practical for routine analysis. As a result, many chemical and physical techniques have been devised in an effort to quantify oxidative deterioration and to correlate the data with off-flavor development. Chemical methods include those which measure peroxide value, the thiobarbituric acid test, the Kreis test, those which measure total and volatile carbonyl compounds, and oxirane determination tests. Physical methods include ultraviolet and infrared spectroscopy, polarography, gas chromatography and refractometry. A more complete review of these various methods for measuring the extent of oxidation can be found in Gray, J. I., J. Amer. Oil Chem. Soc., Vol. 55, pp. 539-546 (1978).
All of the existing chemical methods employ high temperature, or strong acid or solution, which classify them as destructive methods. Prior to the present invention no dry, room temperature, non-destructive objective assay of the storage stability of packaged lipids existed.